1. Field of the Invention
The present invention relates to a mechanism to enable leak testing of a previously sealed vessel, at any time after the vessel has been sealed. The present invention consists of a self-contained source of pressurized gas which can be discharged to the interior of a sealed vessel by a simple mechanical actuation from exterior of the vessel, without the need for any through-container valving to supply the source of pressurized gas. The invention generally relates to leak testing, and has a particular utility for testing the seal of containers which contain hostile materials, such as nuclear waste.
2. Description of the Prior Art
The present invention deals with a mechanism that has particular utility in the field of leak detection of sealed containers. The present mechanism has particular utility in connection with leak testing of sealed vessels which contain highly harmful materials, such as carcinogenic materials or radioactive materials. It is known to introduce a source of gas pressure inside a sealed vessel through certain valving arrangements, and then to sniff or otherwise sense or detect exteriorly of the container for leaks. However, one objective of the present invention is to avoid any through-container communications, by employing an integrally mounted housing that includes its own source of high pressure testing gas.
The present invention relates to leak testing of hermetically sealed vessels, and the invention itself is a mechanism for selectively discharging pressurized gas within a hermetically sealed vessel. Accordingly, applicant wishes to make of record certain prior art teachings which are presently known to him, as follows: U.S. Pat. Nos. Crouch, 1,933,791; Slosberg, 2,391,354; Allen, 2,634,814; Hill, 2,682,967; Sullivan, 3,003,349; Roberts, 3,186,214; Rose, 3,247,706; Novak, 3,298,571; Molitor, 3,487,677; Roberts, 3,577,769; Mongodin, 3,645,127; Withrow, 3,865,158; Stenback, 4,080,822.
Various of these prior art patents illustrate devices for discharging gases, and certain other of these prior art patents illustrate, generally, the field of leak testing to which the present invention is directed. While certain of these patents are from nonanalogous areas, a brief commentary of all possibly pertinent prior art is considered appropriate, for a most complete understanding of the present invention.
Hill illustrates a fire extinguisher device which generates internal pressure by piercing a cartridge with a valve that is suspended from the lid of a container. The patents to Allen and Withrow illustrate similar fire extinguisher devices that include an internally mounted source of pressurized gas, which can be released to dispense fluid from within the container. In each of these nonanalogous fire extinguisher devices there is no need for maintaining a hermetic seal both before and during actuation, and the actuator itself relies upon rubber valving seal elements to prevent loss of pressure. Additionally, none of these fire extinguisher patents have any need for a subsequent and positive manner of ascertaining that there has been actuation of an internally mounted pressure source.
Novak illustrates a mechanism for inflating a body, wherein a compressed gas source is located within the body and a valve means is provided to discharge the gas. The Novak teachings relate to a device for filling an inflatable body, and also include neither a positive hermetic seal structure between the actuator and the housing, nor a positive manner of determining that there has been actuation.
Stenback illustrates one method for leak testing a transport vessel which contains radioactive material, and in that sense is analogous to the field of the present invention. Stenback places a source of tracer gas, such as helium, and a separate pressurizing gas into a vessel before it is sealed. The gases mix by a subsequent diffusion mechanism and thereby generate an internal pressure. In contrast, the present invention allows a selective pressure actuation within a hermetically sealed container, without regard to the amount of time which has elapsed since the container was sealed.
Slosberg teaches a method for testing sealed cans for leaks, through adding a block of solid carbon dioxide to the can's liquid contents before sealing. The carbon dioxide diffuses within the can and generates a pressure, which will distend the wall of the can if there is no leak.
Molitor is noted to show one type of system for leak detection, wherein a container is positioned within a larger vessel and then both are evacuated. As is conventional practice, a detector fluid, such as helium, is introduced into the container so that leakage into the larger vessel can be measured by a mass spectrometer. This patent illustrates the field of invention to which the present device is directed, and is noted to illustrate conventional leak-testing techniques.
Likewise, Roberts illustrates a test unit which employs both a tracer gas, and a pressurizing gas which must be introduced into the test unit itself. By contrast, the present invention avoids the necessity of introducing a test gas from an external source. The early patent to Crouch is noted to show that one of the preferred gases employed herein, i.e., helium, is well-known as a medium for leak detection.
Sullivan is noted to illustrate an unrelated manner of revealing leakage of a radioactive material, wherein the material is cladded with an internal space, which holds a warning material. Sullivan illustrates an approach to the problem of radioactive leakage wherein a characteristic smell supplies the warning.
The patent to Rose is noted to illustrate yet another method for testing leaks, and particularly a leak within a nuclear fuel element. The fuel element is subjected to an atmosphere of helium, wherein some of the helium is absorbed. The patent is primarily of interest to show the magnitude of helium leakage which can be measured, and is not considered otherwise pertinent. The patent to Roberts is cited to show a prior art type of system for testing a container, such as freon-containing refrigeration coils, for leaks. A container is positioned within a chamber, and a tracer gas is introduced through a valving member. Any leak consequently shows up in the atmosphere of the chamber, through analysis of the chamber contents. Improvements in the present invention go to the complete avoidance of any external tracer gas, since all tracer gas and actuation means are integrally located within the container.
Finally, Mongodin illustrates one type of hand probe device which can be applied to the exterior of the vessel that has previously been pressurized with the tracer gas. Mongodin is noted simply to illustrate further the field of the present invention, and one type of external sensing device which may be employed to determine whether or not a vessel including the improvements of the present invention has a leak.